Speaking to the Vanity Fair’s royal correspondent Katie Nicholl, a source said: “Either William or Kate do drop off, and they are always very friendly.

“William particularly loves to have a chat with some of the other parents and he works out with some of the mums at the Harbour Club after drop off. He's very chatty and amiable.”

The fitness centre had been a regular haunt for his mum Diana in the 1990s, who was often seen there in her gym kit after he and Prince Charles’ marriage collapsed.

FAMOUS: The gym was made famous by Princess Diana's visits (Pic: GETTY)

GETTING INTO SHAPE: Wills pops by the gym after his school runs (Pic: GETTY)

A source first revealed to the Mail On Sunday in October 2017 that William had signed up to the gym, and that he reportedly asked staff if they still made the special cookies Diana used to buy him as a treat when they went there together.

“He visited the cafe and told staff that Diana would buy a cookie for him as a treat if he’d been behaving well,” a source said at the time.

“The chefs started flapping, saying they’d find the recipe and rustle one up right away, but he said he didn’t want any special treatment.”

BEND IT LIKE BECKHAM: Wills appears to be trying to get fit (Pic: GETTY)

Despite William’s happy memories of the gym, it was also the scene of some heartbreaking experiences for him and his brother Prince Harry.

In 2017 Harry recalled in a documentary a painful moment which occurred with Diana at the club in the 90s surrounded by paparazzi.

He said: “She was so fed up with being chased … on the way to the Harbour Club, she jumped out of the car, and went running up to these guys and shouted and screamed at them while they took photographs of her.

“All I could hear was screaming. William and I looked at each other and stared out of the window. It was hard.”